Radio tuning means



May 27, 1930. B. a. MlNNlUM RADIO TUNING MEANS Filed Oct. 2'7, 1924Patented May 27, 1930,

UNITED STATES I meals-2 PATENT orrlce BYRON B. MINNIUM, OF CHICAGO,ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, 'IO

STORY 86 CLARK RADIO CORR, OF CHICAGO ILLINOIS, A CORPORATION OF DELA-WARE RADIO TUNING IvIEAN'S Application filed October 27, 1924. SerialNo. 745,985. I

This invention relates to radio apparatus, and contemplates certainimprovements for the purpose of more effectively tuning the apparatus,thereby to prevent certain undesir-able effects, especially inreceiving, and

to insure accurate and more delicate adjustment of the apparatus inaccordance with any particular wave length or frequency.

Generally stated, therefore, the object of the invention is to provideimproved means for more accurately and delicately tuning radio apparatusof any suitable known or approved character, but more especially adaptedfor use in tuning apparatus of thls kind in which vacuum tubes areemployed,

in the well known manner.

To the foregoing and other useful ends, the invention consists in thematters hereinafter set forth and claimed, andas shown in theaccompanying drawing, in which the single figure is a diagram of a radioreceiving hookup or circuit arrangement embodying the principles of theinvention.

As thus illustrated, the receiving hookup or circuit arrangement shownis of a well known form, comprising the aerial 1 connected through therepeating coil 2 to the ground at 3, and provided with three vacuumtubes 4:, 5 and 6, together with batteries 7,

8 and 9, connected in the manner shown. The receiving instrument 10 maybe of any suitable known or approved form, and is preferably connectedin circuit as shown.

The improved tuning means, constituting the invention, include theadjustable condenser 11 connected in shunt of the plate 12 and the grid1?) of the vacuum tube 4 previously mentioned; and said tuning meansinclude, also, the similar adjustable condenser 14 connected in shunt ofthe plate 15 and the grid 16 of the vacuum tube 5 previously mentioned.

The coil 17 is connected in series with the stopping condenser 18, andthe two are connected in shunt of the condenser 11, previouslymentioned; and in a similar manner, the coil 19 is connected in serieswith the stopping condenser 20, and the two are connected in shunt ofthe condenser 14: previously mentioned. The condensers 18 and 20 mayeach be of one microfarad capacity, for example, or of any capacity,which. will keep the plate voltage from reaching the grid of each vacuumtube. The adjustable condenser 21 is in shunt of the secondary of thecoil 2, and similar tuning condensers 22 and 23 are provided. for theinput circuits of the tubes5 and G, as shown, and each con denser 21,22, or 23 is adjustable independently of the condensers 11 and 14, forthereby tuning the input circuits of each tube.

WVith this arrangement, and by adjusting the condenser 11, the parallelcircuit comprising elements 11 and 17 and the capacity between the grid13 and the plate 12 may be tuned for any particular incoming frequency;and by adjusting the condenser 14, thesame tuning effect will beobtained in connection with the plate 15 and the grid 16 previouslymentioned. This insures a more accurate and delicate tuning adjustmentthan is ordinarily obtainable, in a receiving apparatus employing vacuumtubes, and tends to insure better reproduction.

Ordinarily, of course, there is nothing in shuntof the plate and thegrid of the vacuum tube or lamp, in radio apparatus of this kind, havingtuning means (such as 21) for the input circuit of a tube, and undersuch circumstances there is quite liable to be a reaction from theoutput circuit of the lamp or tube back into the input circuit of thelamp, so called, producing a disturbance in the receiver or reproducinginstrument, and sometimes preventing the receiving apparatus fromworking properly. In other words, with the ordinary arrangement, whichwould be exemplified by the circuit arrangement shown, but without thecondensers 11 and 14 and the coils 17 and 19 and the condensers'lR and20, there is quite liable to be some d turbance due to the reaction fromthe output circuit of the lamp or vacuum tube, back into the inputcircuit thereof, but with the tuning arrangement shown in shunt of theplate and grid of the lamp or tube, such disturbance is prevented orgreatly reduced. It will be understood of course that coils 17 and 19are inductors of suitable character.

Without disclaiming anything, and With- 'ber, 1924.

out prejudice to any and all novelty shown and described, what I clalmas my 1nvent1on is I 1. Radio receiving apparatus provided with a vacuumtube havinga plate and a grid and a filament, having adjustable tuningmeans providing one and the same shunt path of fixed resistance for allfrequencies or wave lengths to permit feed back connected in shunt ofsaid plate and grid, the input circuit of the tube including thesecondary of a transformer, and adjustable capacity in shunt ofsaidtransformer secondary, adjustable relatively to and independently ofsaid adjustable tuning means, one sine of said capacity being connectedto one terminal of said filament, and the other side of said capacity bwing connected to said grid, whereby the input circuit of said tube maybe tuned by said capacity for different frequencies or wave lengths, andsuch tuning may be improved by said first mentioned tuning means.

2, Apparatus as specified in claim 1, said adjustable tuning meanscomprising an ad justable condenser in' a low resistance and otherwisecontinuous shunt path, and including a stopping condenser and acoil inseries, the coil being arranged in non-inductive relation toall'portions of said apparatus, said adjustable condenser beingconnected in multiple with said coil and stopping condenser, wherebysaid coil and adjustable condenser are in parallel circuits.

3. Apparatus as specified in claim 1, said adjustable tuning meanscomprising an adjustable condenser in a low resistance and otherwisecontinuousshunt path around the grid plate and in series with saidsecondary.

4. Apparatus as specified in claim 1, said tunin means comprising a 0011111 non-1nductive relation to all portions of said apparatus and a fixedcondenser in series.

5. Apparatus as specified in claim 1, said rillllllt having both fixedand adjustable capacity in parallel circuit paths therein. 7

6. Apparatus as specified in claim 1, said tuningmeans having fixedinductance in noninductive relation to all portions of said apparatus.

7. Apparatus as specified in claim 1, said shunt having capacity in 1parallel circuit paths therein.

Specification signed'this 23rd day of Octo- BYRON 'B." MVINNIIUM.

